Comorbidity of interstitial cystitis with other unexplained clinical conditions.

PURPOSE The aims of this review are 1) to consider the hypothesis that interstitial cystitis (IC) is not a single disease entity in all patients by reviewing the evidence for the presence of IC subtypes and for the comorbidity of various unexplained clinical conditions in some patients with IC, and 2) to describe recent results obtained in humans and in cats with severe feline IC (FIC) that suggest the presence of an underlying neuroendocrine abnormality. MATERIALS AND METHODS The IC literature concerning comorbidity with other disorders was reviewed and these findings were compared with those of investigators studying the comorbid disorders and comparable data on cats with FIC. RESULTS A significant overlap of symptoms exists among a number of unexplained clinical conditions and a common stress response pattern of increased sympathetic nervous system function in the absence of comparable activation of the hypothalamic-pituitary-adrenal axis occurs in a subset of patients with many of these conditions. A comparable pattern exists in cats with FIC, which also includes increased corticotropin releasing factor activity and decreased adrenocortical reserve. CONCLUSIONS Further investigation of the stress response system of patients with IC seems merited, which may provide novel approaches to therapy in some patients.